Issue549 topazfc update

[tdcwilliams]

Closes #589.

• nextsim now takes in modified topaz forecast files

  • reprojected into the nextsim stereographic projection
  • depth dimension removed (with https://github.com/nansencenter/nextsim-env/blob/master/data/process/merge_topaz.py, which also selects the desired depth level) making the files much smaller

• also rename the cs2smos filename to remove the v2.2 suffix (uses any version from 2.2-2.4)